ICs have been both decreasing in size and increasing in circuit density for many years. Often the driving force behind these changes has been the consumer's demand for products requiring more memory in a smaller area.
Conventionally, semiconductor dice are formed on a wafer of silicon material that is diced to form multiple bare dice. Each die is then individually packaged in a plastic or ceramic package. Typically, a lead frame supports the die for packaging and provides the lead system for the completed package. FIG. 1 illustrates a conventionally packaged die 10. The packaged die 10 includes a semiconducting substrate 12 formed with various electrical devices. Circuitry 14 is formed on the face of the die 10 to establish electrical communication between the electrical devices formed in the substrate 12 and the outside world. The circuitry 14 includes external bond pads 16 embedded in a passivation layer 18. During a packaging process each bond pad 16 is electrically connected to a corresponding lead 26 of a lead frame 27. The electrical connection includes a wire bond 20 formed on the bond pad 16, a wire lead 22 and a wire bond 24 formed on the lead 26. An encapsulating material 28 protects and insulates the die 12.
The packaged die 10 can be mounted to a printed circuit board (PCB) or other supporting substrate for constructing an electronic device such as a computer. One problem associated with a conventionally packaged die, such as packaged die 10, is that the package takes up a large amount of volume. This can make dense mounting of multiple packaged dice on a supporting substrate difficult to accomplish. This has led to the development of multi chip modules that utilize bare or unpackaged semiconductor dice. However, because bare dice are thin and fragile, packages called connectors have been developed to electrically connect and house multiple bare dice for mounting a supporting substrate to a printed circuit board. U.S. Pat. No. 5,104,324 to Grabbe et al. is one example of a "Multichip Module Connector" for bare dice.
One problem with this type of connector is that it is difficult to make a reliable electrical connection to the bare die. In addition, the bare die is often damaged during insertion into the connector. Accordingly, there is a need in the art for improved methods for packaging semiconductor dice that permit dice to be more densely packaged on a substrate and a reliable electrical connection to be made without damaging the dice.
In view of the foregoing, it is an object of the present invention to provide an improved method for packaging semiconductor dice. It is yet another object of the present invention to provide an improved method for packaging semiconductor dice that uses an additional protective layer to protect the face of a die and the circuits formed thereon from damage. It is a still further object of the present invention to provide an improved method for packaging a conventional bare semiconductor die and for making a reliable electrical connection to bond pads on the die.
Other objects, advantages and capabilities of the present invention will become more apparent as the description proceeds.